Method for inhibiting grass seed germination with carbamoylmethyl phosphorothioates



United States Patent METHOD FOR INHIBITING GRASS SEED GERMI- NATION WITH CARBAMOYLMETHYL PHOS- PHOROTHIOATES I Angelo John Speziale and John P. Chupp, Kirkwood, M0.,

assignors to Monsanto Chemical Company, St. Louis,

Mo., a corporation of Delaware No Drawing. Filed Nov. 8, 1960, Ser. No. 67,835

9 Claims. (Cl. 712.7)

or oxygen, preferably sulfur), and wherein R and R' are like or unlike radioals of the structure A(IJ =C-G B E a I wherein A is a divalent alkylene radical having the empirical formula C I-I wherein n. is a whole number from 1 to 3, wherein B is halogen or --(CH H wherein b is an integer from 0 to 2, wherein E is halogen. or (CH H wherein e is an integer from 0 to 2, wherein G is halogen or -(C H I-l'. wherein g is an integer from 0 to 2, and wherein the sum total of he and g (i.e.

b-I-e-l-g) is a whole number from 1 to 3, inclusive.- As

illustrative of R" and R are lallyl, methallyl, ethallyl, but-2-enyl, but S-enyl, n-pent-Z-enyl, n-pent-3-enyl, isopent-Z-enyl, 2-chloroallyl, 2-bromoallyl, 3-chloroallyl, 2,3-

dichloroallyl, -2,3,3-trichloroallyl, 3-chloro-but-2-enyl, 2,3- dichlorobut-Z-enyl, etc. It is preferred that R and R =be straight chain galkyl radicals containing 2 to 3 carbon atoms (i.e. ethyl or n-propyl) and that R and R' be alk-Z-enyl hydrocarbon radicals containing from 3 to 5 carbon atoms, particularly allyl.

The carb-am'oylrnethyl phosphorothioates of this'invention can he prepared by reacting a salt (i.e. ammonium or alkali metal such as sodium, potassium or lithium) ofa" phosphorothioic acid of. the structure B G? PSH 'wherein R, R and X have the aforedescribed significance with a substantially equirnolecular proportion of a halide of the structure and wherein D is ahalogen having an atomic number in the range of 16 to 36 (i.e. chlorine or bromine, preferably chlorine). Where and when desired an inert organic solvent (e.g. acetone, but-anone, benzene, toluene, xylene,

dioxane, etc.) can be employed. While a wide range. of reaction temperatures can be employed provided the systern is fluid (i.e. a reaction temperature above the freezing point of the system up to and including the boiling point of the system) it is preferred to employ a reaction temperature. in the range of from about 205C. to about 120 C.

, aieznze Patented Aug. 27, 1963 2 As illustrative of the preparation of the compounds of this invention but not limitative thereof is the following:

EXAMPLE I To a suitable reaction vessel equippedwith a thermom eter, agitator and reflux condenser is charged approximately 22.3 parts by weight (substantially 0.11 mol.) of ammonium 0,0-diethyl phosphorodithioate, approximately 17.3 parts -by weight (substantially 0.10 mol.) of alpha-,

chloro N,N-dia1lyl acetamide, and approximately 160 parts 'by weight of acetone. I The so-charged mass while agitating is heated to the reflux temperature and then refluxed for about 4 hours. The reaction mass is cooled to room temperature and filtered. The filter cake is washed with acetone, the washings combined with the original filtrate, and the solution stripped of acetone under vacuum. The residue is then taken up with methylene dichloride, and the solution so obtained washed first with 5% aqueous sodium carbonate and then with water. Upon stripping under vacuum the methylene dichloride fromthe sowashed solution there is obtained 29.6 parts by weight of,

0,0-diethyl S-(N,N-diallylcarbarnoylmethyl) phosphoro- I dithioate l an oil which is soluble in acetone'but insoluble in water.

Analysis. Theory: 19.8% S, 9.6% P, 4.34% N. Found: 19.2% S, 9.4% P, 4.6% N. a i

Employing the procedure of Example I but replacing alpha-chloro N,N-diallyl acetamide with an equimolecular amount of alpha-chloro N,N-di(2-chloroallyl) acetamide there is obtained 0,0-diethyl S-[N,N-di(2-chloroallyl) car-bamoylmethyl] phosphorodithioate, which is insoluble in water.

' EXAMPLE II To a suitable reaction vessel equipped with a thermometer, agitator and reflux condenser-is charged approximately 22.5 parts by weight-(substantially 0.12 mol.) of ammonium 0,0-diethyl phosp'horothioate, approximately 17.3 partsiby weight (substantially 0.10 mol.) of alphachloro-N,N-diallyl acetamide, and approximately 160 parts by weight of acetone. The so-charged mass while agitating is heated tothe reflux temperature and then refluxed for about 4 hours. The reaction mass is cooled to room temperature and filtered. The filter cake is washed i wherein R" and R' have the aforedescribed significance 7 aqueous sodium carbonate and then with water. stripping under vacuum the methylene dichloride from the v with acetone, the washings combined with the original filtrate, and the solution stripped of acetone under vacuum. The residue is then taken up with methylene dichloride and the solution so obtained washed first with 5% so-washed solution there is obtained 29.2 parts by weight of 0,0-diethy1 S-(N,N-diallylcarbamoylmethyl) phosphorothioate v 7 an oil which is soluble in acetone =but insoluble in water.

Employing the procedure of Example II but replacing ammonium 0,0-diethyl phosphorothioate with an equimolecular amount of potassium 0,0 di-n-propyl phosphorothioate there is obtained as a water-insoluble ,oil 0,0-di-n-propyl S-(N,N-diallylcarbamoylmethyl) phosphorothioate.

Employing the procedure of Example 11 above but replacing alpha-chloro N,N-diallyl acetamide with an equimolecular amount of alpha-bromo N,N-di(2-chloroallyl) acetamide there is obtained 0,0- diethyl S-[N,N-'di(2- chloroallyl)carbatmoylmethyl] phosphorothioate, which is insoluble in water.

Upon

3 EXAMPLE 111 To a suitable reaction vessel equipped with a thermometer, agitator and reflux condenser is charged approximately 30 parts by weight of ammonium 0,0-di-n-propyl phosphorodithioate, approximately 17.3 parts by weight (substantially :1 mol.) of alpha-chloro, N,N-diallyl acetamide, and approximately 80 parts by weight of acetone. The so-changed mass while agitating is heated to the reflux temperature and then refluxed for about 4 hours The reaction mass is cooled to room temperature and filtered. The filter cake is washed with acetone, the washings combined with the orginal filtrate, and the solution stripped of acetone under vacuum. The residue is then taken up (With methylene dichloride, and the solution so obtained washed first with aqueous sodium carbonate and then with water. Upon stripping under vacuum the methylene dichloride from the so-washed solution there is obtained 33.6 parts by weight of 0,0-di-n-propyl S- (N,N-diallylcarbamoylmethyl) phosphorodithioate an oil which is soluble in acetone but insoluble in water.

Analysis.'Iheory: 8.42% P, 18.1% S. Found: 8.84% P, 18.2% S.

Employing the procedure of Example HI but replacing alpha-chloro N,N-diallyl acetamide with an equimolecular amount of alpha-bromo N,N-dibut- -enyl acetamide there is obtained as a water insoluble oil O,-O-di-n-propyl S- (N,N-dibut-2-enylcarbamoylmethyl) phosphorodithioate.

EXAMPLE IV To a suitable reaction vessel equipped with a thermometer, agitator and reflux condenser is charged approximately 26.6 parts by weight (substantially 0.115 mol) of ammonium 0,0-diisopropyl phosphorodithioate, approximately 17.3 parts by weight (substantially 0.1 mol.) of alpha-chloro N,N-diallyl acetamide, and approximately 80 parts by Weight of acetone. The so-charged mass While agitating is heated to the reflux temperature and then refluxed for about 4 hours. The reaction mass is cooled to room temperature and filtered. The filter cake is washed with acetone, the washings combined with the orginal filtrate, and the solution stripped of acetone under vacuum. The residue is then taken up with methylene dichloride, and the solution so obtained washed first with 5% aqueous sodium carbonate and then with water. Upon stripping under vacuum thernethylene dichloride from the so-twashed solution there is obtained 34.6 parts by weight or 0,0-diisopropyl S-(N,N-dial1y1carbamoylmethyl phosphorodithioate [(CHa)20H0]z-SCHzii-N-(CH2CH=CH2)2 an oil which is soluble in acetone but insoluble in water.

Analysis.-Theory: 8.84% P, 18.2% S. Found: 8.25% P, 17.9% S.

Employing the procedure of Example IV but replacing ammonium 0,0-diisopropyl phosphorodithioate with an equimolecular amount of potassium O',O-diisobutyl phosphorothioate there is obtained as a water-insoluble oil 0,0-diisobutyl S-l(N,N-diallylcarbamoyhnethyl) phosphorothioate.

EXAMPLE V To a suitable reaction vessel equipped with a thermometer, agitator and reflux condenser is changed approximately 298 parts by weight (substantially 0.115 mol.) of ammonium 0,0-di-n-butyl phosphorodithioate, approximately 17.3 parts by weight (substantially 0. 1 mol.) of alpha-chloro N,N-dially1 acetamide, and approximately 160 parts by weight of acetone. The so-charged mass While agitating is heated to the reflux temperature and then refluxed for about 4 hours. The reaction mass is cooled to room temperature and filtered. The filter cake methyl) phosphorodithioate an oil which is soluble in acetone but insoluble in water. Analysis.Theory: 8.2% P, 16.9% S. Found 7.95% P, 16.6% S.

EXAMPLE VI To a suitable reaction vessel equipped with a thermometer, agitator and reflux condenser is charged approximately 19.2 parts by weight (substantially 0.11 mol.) of ammonium 0,0-dimethyl phosphorodithioate, approximately 17.3 parts by weight (substantially 0.1 mol.) of alpha-chloro N,N-diallyl acetamide, and approximately parts by weight of acetone. The so-charged mass while agitating is heated to the reflux temperature and then refluxed for about 4 hours. The reaction mass is cooled to room temperature and filtered. The filter cake is washed with acetone, the washings combined with the original filtrate, and the solution stripped of acetone under vacuum. The residue is then taken up with methylene dichloride, and the solution so obtained Washed first with 5% aqueous sodium carbonate and then with water. Upon stripping under vacuum the methylene dichloride from the so-washed solution there is obtained 25.1 parts by Weight of 0,0-dimethyl S-(N,N-diallylcarbamoylmethyl) phosphorodithioate S (CH3O)z-l SCH1 N(CHzCH=CHz)a an oil which is soluble in acetone but insoluble in water.

Employing the procedure of Example VI but replacing alpha-chloro N,N-diallyl acetamide with an equimolecular amount of alpha-bromo -N,N-di(2,3-dichlorobut-2-enyl) acetamide there is obtained 0,0-dimethyl S-[N,N-di(2,3- dichlorobut-Z-enyl) carbamoylmethyl] phosphorodithioate, which is insoluble in water.

EXAMPLE VII To a suitable reaction vessel equipped with a thermometer, agitator and reflux condenser is charged approximately 23.1 parts by weight (substantially 0.10 mol.) of ammonium 0,0-di(2-methoxyethyl) phosphorodithioate, approximately 15.6 parts by Weight (substantially 0.09 mol.) of alpha-chloro tN,N-diallyl acetamide, and approximately 80 parts by weight of acetone. The so-charged mass while agitating is heated to the reflux temperature and then refluxed for about 4 hours. The reaction mass is cooled to room temperature and filtered. The filter cake is washed with acetone, the washings combined with the original filtrate, and the solution stripped of acetone under vacuum. The residue is then taken up with methylene dichloride, and the solution so obtained washed first with 5% aqueous sodium carbonate and then with water. Upon stripping under vacuum the methylene dichloride from the so-washed solution there is obtained 31.7 parts by weight of 0,0-di(2-methoxyethyl) S-(N,N- diallylcarbamoylmethyl) phosphorodithioate (CHaO CH2CHaO)21 -SCHz-( iN (CHzCH=CH2)z an oil which is soluble in acetone but insoluble in water. Analysis.'Iheory: 8.1% P, 16.7% S. Found: 7.9% P, 16.1% S.

Employing the procedure of Example VII but replacing ammonium 0,0-di(2-methoxyethyl) phosphorodithioate with an equimolecular amount of sodium 0,0-di(2-ethtemperature and then refluxed for about 4 hours.

s" oxyethyl) phosphorodithioate there is obtained as a water-insoluble oil 0,0-di(2-ethoxyethyl) S-(N,N-diallylcarbarnoylmethyl) phosphorodithioate.

The methods by which the carbamoyl' phosphorothi-' oates of this invention are isolated from reaction mixtures containing same will vary slightly with the reactants employed and the product produced. Further purification by solvent extractions or by absorptive agents such as activated carbon or clays can precede the removal of the inert organic solvent. Additionally an inert organic solvent can be added also in the purification by absorptive agents. However, in general the reaction product is satisfactory for herbicidal purposes without further purification.

The carbamoyl phosphorothioates of this invention are useful for inhibiting the germination and preemergent growth of plants from seeds in contact with soil. In

order to illustrate their activity with respect to analogs.

thereof the following carbamoyl phosphorothioates were prepared.

EXAMPLE A To a suitable reaction vessel equipped with a thermometer, agitator and reflux condenser is charged approximately 15.5 parts by weight (substantially 0.05 mol.) of ammonium 0,0-dicyclohexyl phosphorodithioate, approximately 7.8 parts by weight (substantially 0.045 mol.) of alpha-chloro N,N-diallyl acetamide, and approximately 80 parts by weight of acetone. The so-charged mass while agitating is heated to the reflux temperature and then refluxed for about 4 hours. The reaction mass is cooled to room temperature and filtered. The filter cake is washed with acetone, the washings combined with the original filtrate, and the solution stripped of acetone under vacuum. The residue is then taken up with methylene dichloride, and the solution so obtained washed first with 5% aqueous sodium carbonate and then with water. Upon stripping under vacuum the methylene dichloride from the so-washed solution there is obtained 19 parts by weight of 0,0-dicyclohexyl S-(N,N-diallylcarbamoylmethyl) phosphorodithioate an oil which is soluble in acetone but insoluble in water. Analysis.-Theory: 7.2% P, 14.8% S. Found: 7.0% P, 14.4% S. I

EXAMPLE B To a suitable reaction vessel equipped with a ther-' morneter, agitator and reflux condenser is charged approximately 1-8.4 parts by weight (substantially 0.05 mol.) of ammonium 0,0-di(4-chlorophenyl) phosphorodithio-ate, approximately 7.8 parts by weight (substantially 0.045 mol.) of alpha-chloro N,N-diallyl acetamide, and approximately 80 parts by weight of acetone. The so-charged mass While agitating is heated to the reflux The reaction mass is cooled to room temperature and filtered. Thelilter cake is washed with acetone, the washings combined with the original filtrate, and the solution stripped of acetone under vacuum. The residue is then taken up with methylene dichloride, and the solution so obtained washed first with 5% aqueous sodium carbonate and then with water. Upon stripping under vacuum the methylene dichloride from the so-washed solution there is obtained 22.4 parts by weight of 0,0-di(4-:chlorophenyl) S-(N,N- diallylcanbamoylmethyl) phosphorodithioate an oil which is soluble in acetone but insoluble in water. Analysis.'I'-heory 6.3% P, 13.1% S, 14.5% C1. Found: 6.3% P, 13.1% S, l4.9%-Ol.

As aforementioned the carbarnoylmethy-l phosphorothioates of this invention are useful fior inhibiting the germination and preemergent growth of plants from seed in contact with soil and to illustrate their relative activity in soil the following test procedure was employed.

Seeds of several difierent plants (itemized hereinafter) each representing a principal botanical species are planted in aluminum pans (9%" x 5%" x 2%"). A good grade of top soil treated with 0.05% of a resinous polyelectrolyte soil conditioner is compacted to a depth of /8" from the top of the pan. The grass seeds are scattered randomly lover one-half of the soil surface and the broadleaf seeds are scattered randomly over the remaining one-half of the soil surface. The seeds are then covered with of the prepared soil mixture and the pan leveled.

The leveled surface of the soil in the pan is then sprayed with 15 cc. of acetone containing the test compound dissolved therein at a definite rate in lbs. per acre.

A fter spraying the soil surface, the pan is placed in a sand bench and /2" of water added to the bench. The soil absorbs moisture through perforations in the bottom until the soil surface is about one-half moist, by which time the excess water in the sand bench is drained off.

The remaining soil surface is moistened by capillary action. 7

Fourteen days after application of the test'compound (Germination rates are established for all new seed lots and periodic checks run on old seed in current use.) The scale used is as follows:

HERBICIDAL RATING-CONVERSION SCALE Seed Lot, Percent Germination (Control) The relative value of eachvtest compound with respect to its herbicidal effect on each plant is indicated by a number as follows:

0 No. germination inhibition.

1 Slight germination inhibition.

2 Moderate germination inhibition. 3 Severe germination inhibition.

In the following tables of herbicidal evaluation the test'compounds are represented by code letters as follows:

Test Compound Code OKE-diethyl S-(N,Ndiallylcarbamoylmethyl) phosphorodithio- 'a e Y A 0,0-ditehyl S-(N,N-diallylearbamoylmcthyl) phosphorothioate okoh dirtnethyl S-(N,N-diallylcarbamoylmethyl) DhOSDhOlOdl- 10a e. C 0,0-di(2-methoxyethyl) S-(N,N-diallylcarbamoylmethyl) phosphOIOdiThlOflP Table 1 illustrates the germination inhibition obtained upon applying the test compound ata rate of 25 lbs. per acre while Table 11 illustrates the germination inhibition obtained upon applying the test compound at a rate of 5 lbs. per acre.

(Number of plants surviving) Table I EXTENT OF GERMINATION INHIBITION EMPLOYING COMPOUND Plant A I C i E F G Morning Glory 2 3 1 0 Wild Oat 3 3 2 0 0 Brome Grass 3 3 2 3 0 Rye Grass 3 3 3 3 1 nriish 2 2 O 0 0 Sugar Beet 3 3 2 2 0 Foxta'l 3 3 3 3 3 Grab Grass 3 3 3 3 3 Pigweed 3 3 3 3 3 Soybean 2 3 0 0 1 Wild Buckwheat... 3 3 2 0 0 Tomato 3 3 1 0 0 Sorghum 3 3 3 3 0 ii-severe; 2-moderate; 1slight; 0no.

Table II EXTENT OF GERMINAIION INHIBITION EMPLOYING COMPOUND Plant A B C D l E F G 4 J K 3 1 2 0 0 0 0 0- 0 3 3 1 1 l 0 O 0 0 3 3 2 0 0 0 0 0 0 3 3 3 3 3 0 0 0 0 2 0 l 0 0 0 0 0 0 3 2 2 0 2 0 0 0 0 3 3 3 3 3 3 3 0 0 3 3 3 3 3 3 3 0 0 3 3 3 3 3 3 1 0 0 3 3 2 O 0 l 0 0 0 3 0 0 0 0 0 0 0 0 3 2 2 0 3 0 0 0 0 Sorghum 3 3 3 2 3 2 0 0 0 3severe; 2-moderate; 1sllght; 0no.

To further illustrate this invention seeds of several different plants (itemized hereinafter) each representing a principal botanical species are planted in aluminum pans (9%" x x 2%). A good grade of top soil which has been treated with 0.05% of a resinous polyelec' trolyte soil conditioner is compacted to a depth of from the top of the pan. The grass seeds are scattered randomly over one-half of the soil surface and the broadleaf seeds are scattered randomly over the remaining onehalf of the soil surface. The seeds are then covered with 450 grams of the aforementioned top soil in intimate admixture with the test compound and the pan leveled. The amount of test compound so added is equivalent of an application rate of one pound per acre.

After leveling the soil surface, the pan is placed in a sand bench and /2" of water added to the bench. The soil absorbs moisture through perforations in the bottom until the soil surface is about one-half moist, by which time the excess water in the sand bench is drained off. The remaining soil surface is moistened by capillary action.

Fourteen days after application of the test compound the results are observed and recorded. The number of plants of each species which germinated and grew are counted and converted to a herbicidal rating by means of a fixed scale based on average percent germination. (Germination rates are established for all new seed lots and periodic checks run on old seed in current use.) The scale used is as follows:

HERB ICIDAL RATING-CONVERSION SCALE The relative value of each test compound with respect to it herbicidal effect on each plant is indicated by a number as follows:

In the following table of herbicidal evaluation the test compounds have the same code letter significance as described hereinbefore:

Table III EXTENT OF GERMINATION INHIBITION EMPLOYING COMPOUND Plant WOHQMCOWMHWWOO OOQHNOJNOOWON NOOOONJMOOOJNO OOQQOWWQQNQQ NONOONNOQCOQDO 1 3severe; 2-moderato; 1-slight; 0no.

From the foregoing evaluation data it is apparent that the carbamoyl phosphorothioates are effective pro-emergence herbicides.

From the above tables :of data it will be evident that the herbicidal action of the carbamoyl phosphorothioates of this invention are unusual, since near analogues not within the scope of this invention are relatively useless as herbicides. Valuable herbicidal effects will be observed by applications of small amounts, for example, as low as 0:10 lb. of active component per acre as well as high concentrations, for example lbs. per acre. The selective activity on grasses is exhibited at lower rates of application, for example from 0.5 to 10 lbs. per acre. For general application and herbicidal effect on both the grasses and dicotyledonous plants, it will be found necessary to use from 10 to '50 lbs. per acre.

Selective herbicidal activity with respect to several genera of grasses is illustrated by the data in Table III. Other experiments run with respect to plants of different genera, which have different metabolisms and physical characteristics indicate little or no inhibition of growth. The botanical types, or genera, of grasses which are effectively controlled by means of the phosphorothioates of this invention, embrace a large number of undesirable plants, or weeds, frequently found in vegetable crops. This invention, however, is not limited to removing the grasses from broad leaf plants since the selective activity will be useful in removing weeds from corn, which belongs to a different genus of grass. Many other crops and particularly the broad leaved plants are inhibited by weeds of the crab grass and rye genera, which can be effectively controlled by the practice of this invention. In some instances there are minor herbicidal effects on dicotyledonous plants, and therefore \optimum results may depend to some extent on experience with respect to the activity of the particular carbamoyl phosphorothioate on the vegetable crop to be treated.

It will be apparent that quite different effects can be obtained by modifying the method of use. For this reason an essential part of this invention is the formulation so as to permit a uniform predetermined application of herbicide to soil or other growth media so as to produce the desired effect. By proper selection and proportioning of the various extending agents either liquid or solid formulations can be prepared, and so as to adapt the herbicide for achieving the desired result with any conventional device for treating the surface or sub-surface of the soil or other growth media.

Although the phosphorothioates of this invention are useful per se in controlling the germination and preemergent growth of a wide variety of plants, it is preferable that they be supplied to the soil or other plant growing media in a dispersed form in a suitable extending agent.

In the instant specification and appended claims it is to be understood that the term dispersed is used in its widest possible sense. When it is said that the phosphorothioates of this invention are dispersed, it means that the particles of the phosphorothioates of this invention may be molecular in size and held in true solution in a suitable organic solvent. It means further that the particles may be colloidal in size and distributed throughout a liquid phase in the form of suspensions or emulsions or in the form of particles held in suspension by wetting agents. The term dispersed also means that the particles may be mixed with and distributed throughout a solid carrier providing a mixture in particulate form, e.g. pellets, granules, powders, or dusts.

In the instant specification and appended claims it is to be understood that the expression extending agent includes any and all of those substances in which the phosphorothioates of this invention are dispersed. It includes therefore, the solvents of a true solution, the liquid phase of suspensions, or emulsions and the solid phase of particulate solids, e.-g. pellets, granules, dusts and powders.

The exact concentration of the phosphorothioates of this invention employed in combatting or controlling noxious vegetation can vary considerably provided the required dosage (i.e. herbicidal amount) thereof is supplied to the plant growing medium. From a practical point of view, the manufacturer must supply the agriculturist with a low-cost concentrate or spray base or particulate solid base in such form that, by merely mixing with water or solid extender (e.'g., powdered clay or talc) or other low-cost material available to the agriculturist at the point of use, he will have an easily prepared herbicidal spray or particulate solid. In such a concentrate composition, the phosphorothioate generally will be present in a concentration of to 95 percent by weight, the residue being any one or more of the well-known herbicidal adjuvants, such as the various surface active agents (e.-g. detergents, a soap or other emulsifying or wetting agent), surface active clays, solvents, diluents, carrier media, adhesives, spreading agents, humectants, and the like.

There are a large number of organic liquids which can higher liquid alkanes, hydrogenated naphthalenes, solvent naphtha, benzene, toluene, xylene, petroleum fractions (e.g. those boiling almost entirely under 400 F. and having a flash point above about 80 F., particularly kerosene), mineral oils and the like.

The phosphorothioates of thi-sinvention are preferably supplied to the plant growing medium in the form of emulsions or suspensions. Emulsions or suspensions are prepared by dispersing the phosphorothioate of this invention either per se or in the form of an organic solution thereof in water with the aid of a water-soluble surfactant. The term surfactant as employed here and in the appended claims is used as in volume II of Schwartz, Perry and Berchs Surface Active Agents and Detergents (1958, lnterscience Publishers, Inc., New York), in place of the expression emulsifying agent, to connote generically the various emulsifying agents, dispersing agents, wetting agents and spreading agents" that are adapted to be admixed with the active compounds of this invention in order to secure better wetting and spreading of the active ingredients in the water vehicle or carrier in which they are insoluble through lowering the surface tension of the water (see also Frear, Chemistry of Insectides, Fungicides and Herbicides, second edition, page 280). These surfactants include the well-known capillary active substances which may be anion-active (or anionic), cation-active (or cationic), or non-ionizing or (non-ionic) which are described in detail in volumes I and -II of Schwartz, Perry and Bero'hs Surface Active Agents and Detergent-s 1958 Interscience Publishers, Inc., New York), and also in the November 1947 issue of Chemical Industries (pages 8l1824) in an article entitled Synthetic Detergents by John W. Mc- Cutcheon and also in the July, August, September and October 1952 issues of Soap and Sanitary Chemicals under the title Synthetic Detergents. The disclosures of these articles with respect to surfactants, ie the anionactive, cation-active and non-ionizing capillary active substances are incorporated in this specification by reference in order to avoid unnecessary enlargement of this specification. The preferred surfactants are the water-soluble anionic surface-active agents and the water-soluble nonionic surface-active agents set forth in US. 2,846,398 (issued August 5, 1958). In general it is preferred that a mixture of water-soluble anionic and water-soluble non-ionic surfactants be employed.

The phosphorothio-ates of this invention can be dispersed by suitable methods (e.g. tumbling or grinding) in solid extending agents either organic or inorganic in nature and supplied to the plant growing medium in particulate :form. Such solid materials include for example, tricalcium phosphate, calcium carbonate, kaolin, bole, kieselguhr, talc, bentonite, fullers earth, pyrophilli-te, diatomaceous earth, calcined magnesia, volcanic ash, sulfur and the like inorganic solid materials and include for example, such materials of organic nature as powdered cork, powdered wood, and powdered walnut shells. The preferred solid carriers are the adsorbent clays, e. g. bentonite. These mixtures can be used for herbicidal purposes in the dry form or by addition of water-soluble surfactants or wetting agents; the dry particulate solids can be rendered wettable by water so as to obtain stable aqueous dispersions or suspensions suitable for use as sprays. I

In all of the forms described above the dispersions can be provided ready for use in combatting noxious vegetation or they can be provided in a concentrated form suitable for mixing with or dispersing in other extending agents. As illustrative of a particularly useful concentrate is an intimate mixture of phosphorothioate of this invention with a water-soluble surfactant which lowers the surface tension of water in the weight proportions of 0.1 to 15 parts of surfactant with sufiicient of the phosphorothioate of this invention to make 100 parts by weight. Such a concentrate is particularly adapted to be made into aspray for combatting various forms of noxious vegetation by the addition of water thereto. As illustrative of such a concentrate is an intimate mixture of parts by weight of 0,0-diethyl S-(N,N-diallylcarbamoylmethyl) phosphorodithioate and 5 parts by weight of a water-soluble non-ionic surfactant such as the polyoxyethylene derivative of sorbitan monolaurate.

Another useful concentrate adapted to be made intoa spray for combatting noxious vegetation is a solution (preferably as concentrated as possible) of a phosphorothioate of this invention in an organic solvent therefor. The said liquid concentrate preferably contains dissolved therein a minor amount (e.g., 0.5 to 10 percent by weight of the weight of the new herbicidal agent) of a surfactant (or emulsifying agent), which surfactant is also Water-soluble. As illustrative of such a concentrate is a solution of 0,0-di-n-propyl S-(N,N diallylcarbamoyl-v 1 l glycol non-ionic surfactant and a water-soluble alkylaryl sulfonate anionic surfactant.

Of the surfactants aforementioned in preparing the various emulsifiable, wettable or dispersible compositions or concentrates of this invention, the anionic and nonionic surfactants are preferred. Of the anionic surfactants, the particularly preferred are the well-known watersoluble alkali metal 'alkylaryl sulfionates as exemplified by sodium decylbenzene sulfonate and sodium dodecylbenzene sulfonatc. Of the non-ionic surfactants the particularly preferred are the water-soluble polyoxyethylene derivative of alkylphenols (particularly isoctylphenol) and the water-soluble polyoxyethylene derivatives of the mono-higher fatty acid esters of sorbitan containing 15 to 30 moles of ethylene oxide per mole of sorbitan monoester of alkylphenol.

-In all of the various dispersions described hereinbefore for herbicidal purposes, the active ingredient can be one or more of the compounds of this invention. The compounds of this invention can also be advantageously employed in combination with other pesticides, including, for example, nematocides, bactericides, and insecticides. In this manner it is possible to obtain mixtures which are etfective against a wide variety of pests and other forms of noxious life.

When operating in accordance with the present invention growth inhibiting amounts of the compound or a composition containing same are dispersed or distributed in any convenient fashion in soil or other growth media, for example by simple mixing with the soil, or by applying to the surface of the soil and thereafter dragging or disking the soil to the desired depth, or by injection or drilling techniques whereby the phosphorothioate of this invention is deposited beneath the surface of the soil, or by employment of a liquid carrier (solvent or nonsolvent) to accomplish the penetration and impregnation. The application of the spray and dust compositions to the surface of the soil may be accomplished by conventional methods, e.g. with power dusters, boom or hand sprayers or spray clusters.

While this invention has been described with respect to certain embodiments, it is to be understood that it is not so limited and that variations and modifications thereof obvious to those skilled in the art can be made without departing from the spirit and scope thereof.

What is claimed is:

'1. The method :of inhibiting the germination and preemergent growth of plants in contact with soil which comprises treating said soil with from 0.5 to 50 pounds per acre of a carbamoyl phosphorothioate of the structure R X R" RIO R!!! wherein R and R are straight chain alkyl radicals containing 2 to 3 carbon atoms, wherein X is a chalkogen of atomic weight less than 40, and wherein R and R are alk-2-eny1 hydrocarbon radicals containing 3 to 5 carbon atoms.

2. The method of inhibiting the germination and preemergent growth of plants in contact with soil which com prises treating said soil with a herbicidal amount of a canbamoylmethyl phosphorothioate of the structure \II II PS-CH1C-N(CH2CH=OH2)2 RO wherein R and R are straight chain alkyl radicals containing 2 to 3 carbon atoms.

3. The method of inhibiting the germination and preemergent growth of plants in contact with soil which comprises treating said soil with a herbicidal amount of 0,0-di-n-propyl S-(N,N-diallylcarbamoylmethyl) phosphorodithioate.

4. The method of inhibiting the germination and pre- 12 emergent growth of plants in contact with soil which comprises treating said soil with a herbicidal amount of 0,0-diethyl S-(N,N-diallylcarbamoylmethyl) phosphorodithioate.

5. The method of selectively inhibiting the germination of grass seeds in contact with soil and the preemergent growth thereof which comprises treating said soil with a herbicidal amount of from 0.5 to 50 pounds per acre of a carbamoyl phosphorothioate of the structure R0 I c 0 R" RIO R!!! wherein R and R are straight chain alkyl radicals containing 2 to 3 carbon atoms, wherein X is a chalkogen of atomic weight less than 40, and wherein R" and R are alk-Z-enyl hydrocarbon radicals containing 3 to 5 carbon atoms.

6. The method of selectively inhibiting the germination of grass seeds in contact with soil and the preemergent growth thereof which comprises treating said soil with a grass growth inhibiting amount of a carbamoylmethyl phosphorothioate of the structure \II II PSCH2CN(CH:CH=CH1)2 wherein R and R are straight chain alkyl radicals containing 2 to 3 carbon atoms.

7. The method of selectively inhibiting the germination of grass seeds in contact with soil and the preemergent growth thereof which comprises treating said soil with a grass growth inhibiting amount of 0,0-diethyl S-(N,N- diallylcarbamoylmethyl) phosphorodithioate.

8. The method of inhibiting the germination and preemergent growth of plants in contact with soil which comprises treating said soil with from 0.5 to 50 pounds per acre of a carbamoylmethyl phosphorothioate of the structure RIO R!!! wherein R and R are selected from the group consisting of alkyl and alkoxyalkyl radicals containing 1 to 4 carbon atoms, wherein X is a chal'kogen of atomic weight less than 40, wherein R and R, respectively, contain from 3 to 5 carbon atoms and are selected from the group consisting of alkenyl, chlorine substituted alkenyl and bromine substituted alkenyl, the respective primary carbon atoms of said R" and R' containing two hydrogen substituents.

9. The method of selectively inhibiting the germination of grass seeds in contact with soil and the preemergent growth thereof which comprises treating said soil with from 0.5 to 50 pounds per acre of a carbamoylmethyl phosphorothioate of the structure RIO R/l/ wherein R and R are straight chain alkyl radicals containing 2 to 3 carbon atoms, Where X is a chalkogen of atomic weight less than 40, and wherein R" and R are alk-2-enyl hydrocarbon radicals containing 3 to 5 carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTS 2,865,801 Baker Dec. 23, 1958 2,959,610 Young et al. Nov. 8, 1960 2,968,669 McCall June 17, 1961 FOREIGN PATENTS 164,112 Sweden July 22, 1958 

1. THE METHOD OF INHIBITING THE GERMINATION AND PREEMERGENT GROWTH OF PLANTS IN CONTACT WITH SOIL WHICH COMPRISES TREATING SAID SOIL WITH FROM 0.5 TO 50 POUNDS PER ACRE OF A CARBAMOYL PHOSPHOROTHIOATE OF THE STRUCTURE 